Let's say that this guy named A kills another guy named B. Let us also say that A meticulously planned the whole thing and then carried out the plan to the T and was successful in murdering B. Mission Accomplished! The Police catch A and get hold of enough evidence to get a conviction. The judge sentences A to death. Let's call the judiciary apparatus C. Now, C is planning to kill A. C has made meticulous preparations to make sure that A dies. Then, C carries out this meticulous plan to the T and is successful in killing A. Pray tell, what's the difference between A and C?
People sometimes say that the mere presence of capital punishment in the judiciary system of a state is a deterrent for people so that less number of murders and killings are committed. However, we can see that capital punishment has not deterred anyone from actually committing a murder because murders are committed in states with capital punishment as rampantly as those without. Therefore, this argument is nullified.
Also, what I think is that the judiciary should not just vengefully mete out slaps on the wrist (or on the neck, for that matter) and make sure that justice really is served. If justice demands an eye for an eye then what's the difference between the civilized world and the Taliban?
Let's say that a person is executed and somewhere in the future, new evidence comes to light that exonerates the person. What does the state do? How does the state make the person come back to life? The state has no right to take what it cannot give back in the event of a mistake committed on its part. If, however, this person were not executed but was kept in a pennitentiary for life (and I mean for life, with no parole), then the state could release them and ask their forgiveness for the time that the state took from them. This is, I think, better than saying sorry to the family of a deceased.
So, it makes one wonder what the difference between capital punishment and murder really is.